Fats & Oils: What to choose for good health? Lesson one: Fats in our food

Lets start at the very beginning, a very good place to start. Gosh I feel all Mary Poppinsish, rest assured I am not Mary Poppins. Although her gorgeous parrot umbrella does lend itself to an incredibly cheesy, christmas cracker style nutrition joke.

Whoops, I’ve just realised I have my Julie Andrews characters muddled. The first line was from the Sound of Music. No matter, lets continue.

A confession

This month I plan to get to the bottom of a question that has been bugging me for quite some time. What are the best fats and oils to be using in cooking for good health? When I studied at the University of Otago 10 years ago, the answer to this question was pretty clear cut. The answer was unsaturated plant based oils. Recently I have noticed there may have been a shift in this advice. I say ‘may’, as most of the information I have seen about fats and oils recently has been what has been popping up in my Facebook newsfeed. And I know, that this is not always the most valid information source. Imagine some of the crazy things you would have done if you trusted all the advice that popped into your news feed.

So I confess in the past couple of years whilst getting to grips with three kiddliwinks, I have not read many clinical papers. I am therefore not up to date, and I don’t know if there has actually been a change in thinking in the nutrition research and medical community when it comes to fats and oils and health. So my plan is to dig deeper, read and evaluate some good recent clinical papers, seek out some actual expert opinions, and come back to you with an answer.

In the mean time lets start with the basics. So that we are all on the same page.

Fats in our food

What foods contain fat?

Animal products contain fat. You will be able to visibly see the fat in meats, chicken and fish (most of it is under the skin). Egg yolks and dairy products contain fat.

Plant based foods also contain fat. Nuts and seeds are high in fat. Some legumes contain significant amounts of fats (Soya beans and Peanuts). Fruits and vegetables are typically fat free, with the exception of olives and avocado.

Some basic biochemistry

The fats and oils we eat although quite different when we look at them (olive oil vs. butter, or coconut oil vs canola oil for example). All actually have a pretty similar chemical structure. They are made up of three fatty acids and glycerol. This is where the word Triglyceride comes from. Triglycerides in essence look like a capital letter E.

A triglyceride looks a bit like this

There are always 3 fatty acids that attach to the glycerol. But there are heaps of different fatty acids, so a triglyceride can have many different fatty acid combinations.

The different fatty acids come about because of two design features

Length

Fatty acids can be long, short or medium in length. Length can have an impact on how they are digested and used for energy by the body.

Saturation

Saturation has absolutely nothing to do with my rather terrible attempt at humour earlier. My parrot in a raincoat joke, in case you had forgotten. Saturation refers to whether they have any double bonds or not in their chemical structure. (Actually it refers to the hydrogen atoms around a double bond, but that’s if we are getting picky)

Saturated fatty acids (SAFA) have no double bonds. This means they are quite straight.

Mono-unsaturated fatty acids (MUFA) have one double bond. This means they have one bend

Poly-unsaturated fatty acids (PUFA) have two or more double bonds. This means they are quite kinked and bent

Double bonds/saturation has an impact on the melting point of a fatty acid. Typically fats that are liquid at room temperature such as oils contain unsaturated fatty acids, MUFA and PUFA. Fats that are solid at room temperature such as lard or coconut oil contain SAFA.

Fatty acids in food

The fats and oils we eat are often classified by saturation. Ie butter is known as a saturated fat, olive oil as monounsaturated. Or by plant or animal source. Plant oils are typically unsaturated while animal fats are generally saturated. In reality, edible fats and oils actually contain a mix of fatty acids. One type might predominate, and give it its classification, but they are typically an eclectic mix.

Trans fatty acids

I am sure you have all heard about how Trans Fats can be bad for health. But what the heck are Trans Fats? Trans fatty acids are a sub group of unsaturated fatty acids.

As I mentioned above an unsaturated fatty acid will have one or more double bond in its structure. This double bond will cause a bend/kink in its shape. Or at least usually it does. It gets a bit technical so I wont go into detail. In a nutshell. There are two ways a double bond can sit in a fatty acid. cis or trans. If it is a cis double bond it will give the fatty acid a bend. If it is a trans double bond the fatty acid will remain quite straight. If an unsaturated fat has a trans double bond it therefore behaves more like a saturated fat. ie. it is a higher melting point and is solid at room temperature. In nature the vast majority of unsaturated fatty acids are cis in nature. Trans fatty acids mainly come about during food manufacture. Where either intentionally, through a process of hydrogenation or unintentionally just through the cooking processes we end up with trans fats. To become a trans fat, a fatty acid must have a double bond in its structure to start with. So only unsaturated fats can become trans fats.

Omega 3 and Omega 6 Fats

Omega 3 and Omega 6 refers to the chemical structure of a fatty acid. It is to do with the position of the last double bond in a polyunsaturated fatty acid. They perform quite different roles in our body, which will be covered in my next article. In the western diet we typically eat more Omega 6 fats, with big contributors being Sunflower, Canola Soya and Palm Oil, although many other foods contain omega 6 fats as well. One of the best sources of omega 3 fats is oily fish.

Essential Fatty Acids

We eat fat, but our body is pretty good at being able to make it as well. (My hips and thighs are great examples!) Apart from two fatty acids which are known as Essential Fatty Acids. They are called essential, because we need them for good health, but our body can’t make them. These two fatty acids are alpha-linolenic acid and linoleic acid. Generally if we are eating a good balanced diet containing oily fish, nuts, seeds and edible oils we will be taking in our quota of the essential fatty acids. Breast milk contains essential fatty acids and they are added into infant formula. Have you ever wondered why we have Vitamins A-E a gap then K. One of the reasons is because of essential fatty acids. At one point they were considered to be a vitamin. I think from memory (old nutrition lectures at Otago University) they were called Vitamin F to begin with. Then they got reclassified and were called essential fatty acids instead.

Right, so there we have it in a nutshell (Ok, I’ll admit a rather big nutshell) Now we are all on the same page when it comes to fats in our foods. What foods have them, and what the different types are. My next article will look at what these different fats do in our body, After that I will start looking at specific edible fats to determine what we should or should’nt be using in our day to day lives.

I plan to cover topics such as

Butter vs Margarine?

Coconut oil, does it live up to the hype?

Fats for frying

Do you have any questions regarding fats and oils? If you do please let me know in the comments below.